Due to light and thin, power saving, and low irradiation features, liquid crystal display panels have gradually replaced conventional cathode-ray tube display devices and are widely used in commercial and consumer electronic products. Based on the driving modes, the liquid crystal display panels may be divided into passive matrix (PM) and active matrix (AM) liquid crystal displays. The PM liquid crystal display includes static and multiplex liquid crystal displays etc, and the AM liquid crystal display mainly includes thin film transistor (TFT) liquid crystal displays at present. For AM liquid crystal display devices, TN (twisted nematic) type has once been popular, but it has the disadvantage of narrow viewing angle. In view of this, MVA (multi-domain vertical alignment) and IPS (in-plane switching) type liquid crystal technologies are now employed in liquid crystal panels with a wide viewing angle.
IPS wide viewing angle technology was developed by Hitachi in 1995. In the technology, a voltage is applied to the electrodes in an IPS mode, so that the liquid crystal molecules originally parallel to the electrodes rotate to an orientation perpendicular to the electrodes, with the major axis of the liquid crystal being still parallel to the substrate. The liquid crystal molecules may be rotated to a desired angle only by controlling the voltage, which may be used in combination with a polarizer to modulate the transmittance of the polarized light, so as to display various color scales. The liquid crystal molecules in IPS mode has a working principle similar to that of the liquid crystal molecules in TN mode, except that the liquid crystal molecules in IPS mode are aligned in a non twist nematic mode, with the major axis being always parallel to the substrate. However, the electrodes should be fabricated into comb-like and aligned on the surface of an underlying layer. This may result in a reduced contrast. Because of the fact that positioning the electrodes on the same plane may lower the aperture ratio and decrease the light transmittance, the brightness of a backlight source must be enhanced. Compared with the conventional TFT-TN type liquid crystal display, the contrast and response time of the IPS type liquid crystal display are not improved.
MVA is a multi-domain vertical alignment technology, which makes use of projections to enable the liquid crystal when in static to deflect to a certain angle, instead of being in conventional vertical pattern. When a voltage is applied to make the liquid crystal molecules horizontal, the backlight can penetrate more quickly, such that the response time can be reduced greatly. Furthermore, the viewing angle is widened because the orientation of the liquid crystal molecules is altered by the projections. The viewing angle can be increased up to above 160 degrees, and the response time is reduced to less than 20 ms.
In an MVA type liquid crystal display device, for the purpose of widening the viewing angle, the liquid crystal molecules are inclined to 4 directions by the applied voltage. Due to the complex protrusion and ITO slit configurations, the light transmittance becomes low. In case that the configurations are simplified, and the interval between the protrusions or the gap of the ITO slits is increased, the light transmittance can be increased. However, if the interval between the protrusions or the gap of the ITO slits is too large, the propagation of the inclination of the liquid crystal molecules becomes much slow, and thus the response becomes very slow.